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bed corners bow print surface
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there is a visible bow to the print surface because the portions of the ninjaflex corners that protrude underneath the bed are too large
If you cut that portion off, the corner itself isn't pushing the glass against the washer; you can wiggle it up and down. So they're higher in the middle and lower at the corners, creating a curve that we're pressing our print surface over.

Event Timeline

logan created this task.Dec 11 2018, 10:56 AM
logan created this object with edit policy "LulzBot Hardware Products (Project)".

With a straight edge (uncertified) set across the bed behind the front two bed leveling washers, using feeler gauges I measure a gap of .406mm on the left and .254mm on the right while there is no gap at the center.

west added a comment.Dec 11 2018, 11:13 AM

We can adjust the corners to press up less. This may also be something we could tackle in the slice by making it more compress-able

I think we should look a little closer at dimensions before messing with the slice. They should be there to support in the event of a sag but I don't think they should apply pressure to the center of the bed. Is there a reason for the portion underneath the bed leveling washer to not be pressing the plate and glass against the washer?

DaniAO assigned this task to west.Dec 12 2018, 10:13 AM
logan added a comment.Dec 12 2018, 2:05 PM

I just noticed that the bed corners tend to protrude in front of the bed plate, they tend to sit at an angle because of the bow on the side of the wiper pad mount.

logan added a comment.Dec 12 2018, 2:22 PM

With the new ones on, without heat cycling yet, the bow seems less but still apparent. With the edge of the machinist square laid across, I can fit a .178mm feeler gauge at the edge of the bed.

logan triaged this task as High priority.Dec 14 2018, 7:32 AM
logan added a comment.Jan 4 2019, 10:57 AM

Latest round of softer bed corners are much better. It did change my Z offset in the center of the bed from -1.3mm (with bed corners that only press on the corners) to -1.1mm with the new ones.
Alpha: -0.3 to -0.4mm in center of bed
Post alpha 1: -0.45 to -0.6 in center of bed
Post alpha 2(softer): -1.1 in center
old style: -1.3 in center

west added a comment.Jan 7 2019, 7:36 AM

@logan looks like the newest version with the "squishy" slice made a considerable difference. I the heater pad drooping at all?

logan added a comment.Jan 7 2019, 8:02 AM

@west Not that I can see, looks good to me.

west added a comment.Jan 8 2019, 12:29 PM

Changes are in branch T4631